Most of the polyols that are used in polyurethane industries originated from petroleum-based chemicals, which can be categorized into two classes (a) hydroxyl-terminated polyethers and (b) hydroxyl-terminated polyesters. The polyether polyols of most interest in polyurethane industries are polypropylene glycols and polytetramethylene glycols, in which their manufacture involves the addition polymerization of the monomeric epoxide. On the other hand, the polyesters are prepared by reaction of dibasic acids with diol or alcohols with higher functionality alcohol.
However, as the world's petroleum resources are depleting coupled with its ever-increasing prices, polyurethane producers worldwide have been looking into renewable/sustainable raw materials to replace petroleum-based polyols. An ideal alternative feed stock will be natural oils and fats, which can derive from both plants and animals sources. Plenty of patent applications have been filed regarding different approaches in producing the polyols from the natural source in order to provide a solution to effectively produce polyols with the desired qualities. Nonetheless, polyols produced by the prior arts are vary in terms of quality as the intermediate product being employed for producing the polyols are not subjected to prior purification.
Nicolás et al. disclosed a patent application in U.S. Pat. No. 6,548,609 regarding a process for obtaining oleochemical polyols from natural oils and/or fats. The disclosed process utilizes a planar Lewis acid for the alcoholysis process and large amount of energy has to be provided during the alcoholysis as the reaction temperature is above 200° C. Due to the drastic condition applied and no purification on the epoxidized oil, the yield of the desired products via the disclosed process is very low as most of the substrates are converted to side products.
U.S. Pat. No. 6,433,121 is another patent disclosed a process to produce vegetable oil-based polyols which can be subsequently used for polyurethane production. In the disclosed process, fluoroboric acid is employed as the catalysts to improve the alcoholysis or hydrolysis of the epoxidized oil. Besides alcohol, water also being used as a reactant to hydrolyze the epoxidized oil. The process disclosed does not include purification or neutralizing step for the epxoidized oil, it is known that acidic condition renders the epoxidized compounds vulnerable to attack from nucleophile such as water. Thus, the process disclosed in this application is unlikely to be used for synthesis long chain polyols or high functionality polyols via reaction between the epoxidized oil with other polyhydric alcohol as most of the epoxidized oil reacts with water molecule first rather than the polyhydric alcohol.
U.S. Pat. No. 6,734,315 filed a process to expoxidize unsaturated compounds using a thin film reactor and no catalyst employed during the epoxidation process. On the other hand, patent MXPA04002965 claims an epoxidation process by using clay as the catalysts to accelerate the alcoholysis process between alcohol compounds and epoxidized oil. Geiger et al. filed an application under US patent no. 2007037953 to claim an epoxidation process using organometallic catalysts instead of conventional organic oxidation reagents such as per-acids. All the above mentioned prior arts have shown no attempt in purifying and/or neutralizing the acidic condition of the epoxidized oil before subjecting the epoxidized oil for alcoholysis to produce high functionality polyols. Therefore, the polyols produced can be varied in terms of quality. Nevertheless, the polyols shall be purified too before incorporated with other chemical compounds in manufacturing polyurethane as the remaining chemical residues are normally capable of initiating polymerization of the monomers which maybe not desired in production of polyurethane.